Large Hadron Collider shuts down for two years of upgrades

Renovations will allow LHC to reach its full design energy, improve detectors.

No, finding the Higgs boson doesn't mean the end of physics. But as of today, no atoms will be smashed at the LHC (the Large Hadron Collider at CERN) for approximately two years. During that time, every piece of hardware around the accelerator's full circumference will get some attention, as will the detectors that track collisions.

The LHC was designed to collide protons with a total energy of 14TeV (Tera-electron Volts), but a catastrophic failure early in its history revealed some of the superconducting connectors within the hardware wasn't up to the task. As a result, the LHC hasn't run collisions at energies above 8TeV. Each of these connectors, which link segments of the pipe that the beam travels within, will be replaced over the next two years. While the machine is shut down, the detectors used to track particles will receive maintenance and upgrades.

We're at the annual meeting of the American Association for the Advancement of Science this week, and there will be updates on the properties of the Higgs, as well as the search for dark matter particles. Hopefully we'll hear more about the work that went on during the physics runs of the past several years.

Not trolling, but can someone explain to me what exactly they hope to...errrr...detect at those high energies? I knew the Higgs Boson was one goal. What do they expect to see at those higher energies?

Those energies allow for the appearance of particles not generated since the Big Bang, so far as we know. For example, about 30% of the mass of the universe is dark matter, which is made of particles we haven't yet detected. If we could make some, that would help, considering that all the visible matter in the universe is only about 1% of the total mass.

It's really not what we expect to see that's so exciting. It's the possibility of finding things we didn't expect.

When you're working at the edge of engineering and physics, getting it right the first time is pretty difficult, so I'm not surprised that there are some things that need upgrading after field testing (so to speak).

Not trolling, but can someone explain to me what exactly they hope to...errrr...detect at those high energies? I knew the Higgs Boson was one goal. What do they expect to see at those higher energies?

Those energies allow for the appearance of particles not generated since the Big Bang, so far as we know. For example, about 30% of the mass of the universe is dark matter, which is made of particles we haven't yet detected. If we could make some, that would help, considering that all the visible matter in the universe is only about 1% of the total mass.

It's really not what we expect to see that's so exciting. It's the possibility of finding things we didn't expect.

Maybe I'm just looking at this wrong, but I thought we need to at least "know" what to look after, as we don't see the particles per se, but only their remnants. And we would need at least an explanation what those remnants could be from to determine which particle we created to begin with?

To me, the entire LHC effort looks pretty much like "let's see just how much money and electricity we can waste trying to find something (we don't know what yet) by making things explode at high speed".

For example, about 30% of the mass of the universe is dark matter, which is made of particles we haven't yet detected. If we could make some, that would help...

Playing devil's advocate here -- let's suppose we do make some, what's going to tell us we did?

In other words, how do you detect something you never detected before?

Also, how do you control it if you don't have a fucking clue what it is and how to detect it in the first place?

To me, the entire LHC effort looks pretty much like "let's see just how much money and electricity we can waste trying to find something (we don't know what yet) by making things explode at high speed".

We have a model that takes into account all we know. We then compare the results of the experiments to our model. If they don't match then something is happening not accounted for in our model.

For example, about 30% of the mass of the universe is dark matter, which is made of particles we haven't yet detected. If we could make some, that would help...

Playing devil's advocate here -- let's suppose we do make some, what's going to tell us we did?

In other words, how do you detect something you never detected before?

Thanks to E=MC2, we know that matter can be converted into energy, and vice-versa. So, if some of the energy from the collision ups and disappears (because it got converted into a dark matter particle that we can't detect), then they'll know that one or more dark matter particles were created. If they can work out how many were created, they can divide the missing energy by the number of particles created, which will tell them the mass of the particles. At that point, the theoretical physicists have a field day.

To me, the entire LHC effort looks pretty much like "let's see just how much money and electricity we can waste trying to find something (we don't know what yet) by making things explode at high speed".

And that's why you're not in charge of anything important.

Shhhhhhh. You're talking to someone who seems to have precisely the correct mindset for a future political leader.

Not trolling, but can someone explain to me what exactly they hope to...errrr...detect at those high energies? I knew the Higgs Boson was one goal. What do they expect to see at those higher energies?

As far as the Higgs Boson goes, there is still a lot to learn about it beyond just confirming it's existence. It's exact properties have a fair bit of wiggle room under current theories. As an analogy, we discovered Pluto in 1930 but didn't realize how small it was, or that it was a binary system, until the mid-to-late 70s, and we won't have our first detailed images of it until 2015.

Playing devil's advocate here -- let's suppose we do make some, what's going to tell us we did?

In other words, how do you detect something you never detected before?

It depends on what it is.

If it is something long-lived and that interacts with our detectors via the electromagnetic force, then we'll detect it directly.

If it's something unstable which decays into things we can detect, then we detect those things in excess of what would be predicted in our models. This is how we detected the Higgs -- an excess of certain decay paths than expected in a Higgs-less model.

If it's something stable that doesn't interact with detectors -- something like the Neutralino, the Supersymetric neutrino and a Dark Matter candidate -- then we may infer its existence by seeing fewer particles than expected, or a net momentum of detcted particles, because part of the energy/momentum of the collision went off in the undetected particles. It was similar observations of an energy deficit in certain nuclear reactions that eventually led to the discovery of the neutrino.

Then there's a lot more work to figure out what the properties of these new particles are, and especially in the last case theoretical work to figure out how you might do a better job of detecting them -- e.g. the LHC can only detect neutrinos via the momentum imbalance, but we have dedicated neutrino detector experiments and ones for Dark Matter, should they similarly interact only through the weak force. If the Dark Matter particle interacts only through an as yet unknown Dark (side of the) Force, then it's going to be tough, but maybe we'll figure it out!